Grinding discs



at (mm 0d: 6, 1959 I A I 2,907,146

' GRINDING DISCS I Filed May 21, 1957 THRIF- Iii g E INVENTOR.

ROBERT L. DYAR ATTORNEYS PARKER & CARTER United States Patent GRINDINGDISCS Robert L. Dyar, Milwaukee, Wis., assignor to Milwaukee Motive Mfg.Co., Milwaukee, Wis., a corporation of -Wisconsin Application May 21,1957, Serial No. 660,681 3 Claims. 01. 51-195 This invention relates toabrasive discs and the construction thereof, and more particularly tothe type of abrasive disc employed in grinding the surfaces of metal orother material.

It is manifest to anyone familiar with the art that when abrasive discsare coated with abrasive material adherently attached to the face of thedisc, such coating material tends to prevent flexing of the disc, andwhen too much flexing is applied it would cause the material to crack,and be forced away from the surface of the disc. It is also-manifestthat the material from which the disc is made has a tendency to absorbmoisture, or be affected by temperature variations, causing expansionand contraction, and in this manner the abrasive material and itsadherent agent may be readily torn from the disc and separatedtherefrom.

The principal object of the invention is to overcome the abovementioneddifficulties by providing an abrasive disc consisting of a flat backingplate to which abrasive particles are adherently attached, but separatedin a plurality of individual areas or units.

A further object of the invention is to provide an abrasive disc of thecharacter described so that it may be flexed or bent in any directionwithout affecting the particles of abrasive material adherently attachedto the surface thereof.

Still another object of the invention is to provide an abrasive discwhich has particles of abrasive mixed in a binder of adherent materialand formed into individual areas spaced from each other to admitcirculation of air between the disc surface and the work piece, therebypregenting any matting, or gumming of the surface of the A still furtherobject of my invention is to provide a disc of the character described,in which the abrasive mixed with the adherent binder is formed intoseparate units, permitting the disc to which the abrasive is adherentlyattached to expand, contract or flex, without cracking or fracturing theabrasive surface.

Other and further objects of the invention will become more apparent asthe description proceeds when taken in conjunction with the drawing, inwhich-- Figure 1 shows the working face of an abrasive disc made inaccordance with the invention;

Figure 2 shows an enlarged fragmentary portion of the face of the disc,showing the individual grinding areas or units, separated from oneanother by the V type of groove;

Figure 3 is a fragmentary cross-section of a portion of the disc, coatedwith abrasive material mixed with an adherent agent, and showing onemethod of producing separate surface areas by a forming roll which ispassed over the surface of the disc to form the abrasive material andadherent, agent into individual areas, and exposing the surface of thedisc substantially at the base of each groove;

Figure 4 is an enlarged fragmentary cross-section of a portion of thedisc treated by means of the roller, as shown in Figure 3;

Figure 5 shows a modified form of disc surface in which the groovesbetween individual areas are flattened at opposite sides near the baseto provide a V groove below the flattened portions;

Figure 6 is a fragmentary cross-section of a portion of a disc made inaccordance with the invention, and showing the discflexed to a convexform, with the V grooves spread; and

Figure 7 is a view similar to that shown in Figure 6, but with the discportion flexed in the opposite direction to a concave form, showing theV grooves closing, insteadof spreading as in Figure 6.

Similar characters of reference indicate corresponding parts throughoutthe several views and referring now to the same, the character 10generally shows a circular disc which may be coated on one side, or bothsides, with abrasive particles adherently attached thereto. The disc 11itself may be constructed of fiber cloth, felt, or the like, and mayhave a centrally disposed aperture-12. The abrasive particles aresuitably mixed with an adherent binder, such as glue, applied tothe faceof the disc as .by adding the abrasive particles to the surface of theadherent. The surface of the combined abrasive and adherent agent isscored by' a roller "having V-shapecl blades 13, as shown in Figure 3.Manifestly this scoring is preferably done before the adherent hashardened. The roller may be passed in paths substantially at rightangles to each other, thereby producing V grooves 14 in the working faceof the disc, as seen in Figures 4 and 2. Accordingly, the working faceof the abrasive disc is built up into individual areas or units 15, withthe bottoms 16 of the grooves reaching substantially to the body of thedisc 11. The grooves 14 also provide paths in both directions at rightangles to one another for the passage of air currents when the abrasivedisc is applied to the surface of the workpiece being ground.

The V grooves 14 thereby permit the disc 11 to be readily flexed eitherin concave or convex form, as shown in Figures 6 and 7. This, in Figure6, as the units 15 spread apart from each other, due to the flexing ofthe disc 11, the V grooves 14 will open wider, with the sides spreadapart from each other. The opposite occurs, as shown in Figure 7, whenthe individual units 15 are brought towards each other, the oppositelydisposed sides of the grooves being brought into closer proximity toeach other.

It will be understood further, that disc 11 manufactured of any materialsuitable for the purpose is likely to be affected by atmospheric changesas well as temperature changes. In other words, the disc 11 will expandor contract according to the temperature and according to the humidity,or moisture, if and when applied to the surface. In such cases, however,the individual units 15 of abrasive will be unaffected, but will act asindividual grinding surfaces in performing the function for which thedisc is intended.

Figure 5 shows a modified construction in which the individual abrasiveareas are separated by a groove having a flat stepped surface 17 at eachside, intermediate the outer face and the face of the disc 11. Thegroove 16 is extended in V shape down to the disc surface. Thisarrangement will afford somewhate greater air circulation between theindividual contact areas 15, and will give more room for the particlesto be removed from the surface of the work piece, as they tend to bethrown outward through the grooves due to centrifugal force and thespeed of the revolving disc.

With the novel form of grinding disc herein described, it is possible toget a better abrasive action; it is possible to flex the discs in eitherdirection without fractur- Patentecl Oct. 6, 1.95 9,

ing the adherent material, or the abrasive material held to the disc bymeans of an adherent agent, thus afiording a longer life to the surfaceof the disc, and giving a cleaner surface which will not become coatedso readily by the particles being removed from the workpiece.

Although I have shown and described certainembodiments of my invention,it will be understoodthat I do not wish to be limited to the exactconstruction shown and described, but that various changesandmodifications may be made without departing from. the spirit and scopeof the invention as defined by the appended claims.

I claim:

1. In a circular abrasive disc, a backing disc body formed from flexiblefibrous material, a working face on said disc, said working face beingcomprised of a plurality of working areas of abrasive material particlesmixed with an adherent binder bonding the particles together and theareas to said disc, said working areas being separated by crossed setsof grooves of V-shaped cross section extending at right angles to oneanother, each of said grooves extending rectilinearly across said discand downwardly'from the face of said material to a pointrsubstantiallycoincident with the surface of said body, the grooves of each set beinggenerally parallel to one another and generally parallel to linesextending diametrically of said disc so that the crossed sets provideworking areas of generally uniform size.

.2. The structure of claim 1 wherein the grooves have a stepped V-shapedcross section,

3. The method of making a flexible abrasive disc including the steps offorming a mixture of abrasive material particles and an adherent binderon the surface of a flexible disc body of fibrous material, scoring themixture, before the binder has hardened, with a plurality of equallyspaced V-shaped blades and forming a plurality of generally parallelV-shaped grooves extending parallel to a diameter of said body, thenturning the body and blades relative to one another and similarlyscoring the mixture alonga path at right angles to the path of the firstscoring, the scoring being to a depth such that the bottoms of thegrooves are lo'cated'substantially at the surface ofsaid body so as todivide the abrasive material into individual working areas of generallyuniform size, each of which is' bonded to the body, the disc therebyformed being capable of flexure along the grooves.

References Cited in the file of this patent UNITED STATES PATENTS

